1. Field of the Invention
The present invention relates to a sheet member position correcting device which moves a sheet member in a width direction and corrects a position of the sheet member in the width direction, and an image forming apparatus which has a sheet member position correcting device such as a copying machine, a printer, a facsimile or an MFP.
2. Description of the Related Art
Conventionally, techniques are disclosed of providing a sheet member position correcting device which moves pairs of carriage rollers which are nipping a sheet member in a width direction and corrects positional deviation of the sheet member in the width direction (which is a direction orthogonal to a conveying direction) for an imaging forming device such as a copying machine or a printer (see, for example, Japanese Patent No. 4614243 and Japanese Patent No. 3268329).
Most of these sheet member position correcting devices are each provided with driving rollers and driven rollers which form pairs of carriage rollers which nip and convey sheet members, and moving mechanisms which move the driving rollers and the driven rollers in the width direction. That is, most of the sheet member position correcting devices are each provided with a first moving mechanism which moves the driving rollers in the width direction and a second moving mechanism which moves the driven rollers in the width direction.
In conventional sheet member position correcting devices, two moving mechanisms of the first moving mechanism which moves the driving rollers in the width direction and the second moving mechanism which moves the driven rollers in the width direction are disposed, and therefore the devices become larger and more costly.
To solve such a problem, a measure may be adopted of disposing only moving mechanisms (moving units) which move driving rollers in the width direction without disposing a second driving mechanism which moves the driven rollers.
However, in this case, if the driven rollers are fixed and held such that the driven rollers cannot move in the width direction, when a sheet member nipped by the driving rollers and the driven rollers is moved by the moving mechanisms in the width direction together with the driving rollers, it is not possible to correct the position of the sheet member to move to a target position in the width direction due to sliding friction with the driven rollers.
By contrast with this, if the driven rollers can be moved by friction resistance with the driving rollers in the width direction, when a sheet member nipped by the driving rollers and the driven rollers is moved by the moving mechanisms in the width direction together with the driving rollers, it is possible to correct the position of the sheet member to move to a target position in the width direction. However, when a position of a sheet member having low surface friction resistance is corrected, sliding friction with the sheet member is a little and therefore the driven rollers are not likely to move to the same extent as and together with the sheet member in the width direction and be deviated in the width direction. Further, as such a state is repeated, the positions of the driven rollers in the width direction are significantly deviated from the driving rollers and roller portions of the driving rollers and roller portions of the driven rollers do not abut on each other, and therefore a sheet member cannot be nipped and conveyed by the driving rollers and the driven rollers.
There is needed to solve the above problem, and to provide a sheet member position correcting device and an image forming apparatus which, even when employing a configuration where pairs of carriage rollers formed with driving rollers and driven rollers which nip and convey sheet members are provided and the driven rollers can be driven in the width direction following the driving rollers moved by the moving units in the width direction, corrects the position of the driven rollers in the width direction with respect to the driving rollers without being significantly deviated.